This disclosure relates to integrated cameras and, more particularly, to methods for forming lens plates for integrated cameras.
An integrated camera is a camera formed by integrated device fabrication techniques or processes such as photolithography, ion implantation, diffusion, etching, and other techniques or processes typically used in fabricating semiconductor integrated circuits. Multiple independent, separate integrated camera chips or dies can be fabricated in a single wafer. Integrated cameras are typically very small in size, such that they are suited for applications such as mobile telephones, smart phones, notebook computers, tablet computers, and other similar devices.
Integrated cameras typically include optics such as lenses and other devices used in forming images, as well as a sensor or detector or sensor/detector array for receiving images. To form a high-quality image, the optics of the camera module may include several lenses, which are stacked above the image sensor and are separated by spacers.
The integrated camera is typically manufactured at the wafer level. Under a typical process, a wafer having a plurality of image sensors is first provided. A spacer wafer is placed on the image sensor wafer. The spacer wafer has a plurality of holes aligned with the image sensors. A wafer having a plurality of lenses, known as a lens plate, is then placed on the spacer wafer. The lenses of the lens plate and the holes of the spacer wafer are aligned with the image sensors. A second spacer wafer may be provided before a second lens plate having another plurality of aligned lenses is placed on the wafer stack. Multiple spacer wafers and multiple lens plates may be included in the manufacturing of wafer level cameras. The stacked wafers are diced into individual integrated cameras, each having an image sensor and a stack of spacers and lenses.
FIG. 1 contains a schematic cross-sectional diagram illustrating a conventional lens plate 100. The lens plate 102 includes a glass wafer 102 and a plurality of lenses 104 formed on glass wafer 102. FIG. 2 contains a schematic cross-sectional diagram illustrating two stacked conventional lens plates 202 and 204. The two lens plates 202 and 204 are separated by a spacer wafer 206 stacked between lens plates 202 and 204. The glass wafer plates can adversely affect the quality of the lenses fabricated on the wafers. Also, the light transmission through the glass wafers can adversely affect the brightness and the phase of the light, and, as a result, may degrade the quality of the image formed. These effects can depend on the thickness of the glass wafers. That is, glass wafers with greater thickness will have more pronounced adverse effects on the quality of the lenses and the image formed by the camera.